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PowerPC makecontext

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http://sourceware.org/ml/libc-alpha/2013-08/msg00092.html

Use conditional form of branch and link to avoid destroying the cpu
link stack used to predict blr return addresses.

	* sysdeps/unix/sysv/linux/powerpc/powerpc32/makecontext.S: Use
	conditional form of branch and link when obtaining pc.
	* sysdeps/unix/sysv/linux/powerpc/powerpc64/makecontext.S: Likewise.
This commit is contained in:
Alan Modra 2013-08-17 18:36:45 +09:30
parent 02f04a6c7f
commit 0b2c2ace36
3 changed files with 16 additions and 4 deletions
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6
ChangeLog
View File

@ -1,3 +1,9 @@
2013-10-04 Alan Modra <amodra@gmail.com>
* sysdeps/unix/sysv/linux/powerpc/powerpc32/makecontext.S: Use
conditional form of branch and link when obtaining pc.
* sysdeps/unix/sysv/linux/powerpc/powerpc64/makecontext.S: Likewise.
2013-10-04 Alan Modra <amodra@gmail.com>
* sysdeps/unix/sysv/linux/powerpc/powerpc32/getcontext-common.S: Use

8
sysdeps/unix/sysv/linux/powerpc/powerpc32/makecontext.S
View File

@ -47,7 +47,9 @@ ENTRY(__makecontext)
#ifdef PIC
mflr r0
cfi_register(lr,r0)
bl 1f
/* Use this conditional form of branch and link to avoid destroying
the cpu link stack used to predict blr return addresses. */
bcl 20,31,1f
1: mflr r6
addi r6,r6,L(exitcode)-1b
mtlr r0
@ -136,7 +138,9 @@ ENTRY(__novec_makecontext)
#ifdef PIC
mflr r0
cfi_register(lr,r0)
bl 1f
/* Use this conditional form of branch and link to avoid destroying
the cpu link stack used to predict blr return addresses. */
bcl 20,31,1f
1: mflr r6
addi r6,r6,L(novec_exitcode)-1b
mtlr r0

6
sysdeps/unix/sysv/linux/powerpc/powerpc64/makecontext.S
View File

@ -124,8 +124,10 @@ L(noparms):
/* If the target function returns we need to do some cleanup. We use a
code trick to get the address of our cleanup function into the link
register. Do not add any code between here and L(exitcode). */
bl L(gotexitcodeaddr);
register. Do not add any code between here and L(exitcode).
Use this conditional form of branch and link to avoid destroying
the cpu link stack used to predict blr return addresses. */
bcl 20,31,L(gotexitcodeaddr);
/* This is the helper code which gets called if a function which
is registered with 'makecontext' returns. In this case we